Question about LG 47LN5400 47" LED TV 1920x1080, 120 Hz. HDTV

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Can you tell if LED tv has bad LED strips before changing LED Board/Power Supply (as they're in one piece on a lot of TVs)?

Have sound but no backlight, did flashlight test, can see pic on screen, so it's definitely an LED issue. Can replace LED board/power supply (it's one piece on this model), but it could also be a bad LED strip - is there any way to tell before spending $ on the board/power supply?

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This is not easy to diagnose, either use a meter on the power cable to the led or check the leds one at a time

Posted on Feb 24, 2016

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Posted on Jan 02, 2017

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My TV is Sinotec LED 43 inch HS-2110H-00


The most common problem with backlights in an LED TV set is a failed LED. While these are supposed to last 30,000 - 50,000 hours, they are very sensitive to static electricity damage. This does not show up immediately, but after some time, the LED may flicker, then burn out, or burn out suddenly.

On many LED TV models, the backlight will come on, then turn off if one of the LED strips is bad. Test procedure: unplug the TV set, wait 10 seconds, then plug it back in (or turn off the power strip for 10 seconds if you have the TV plugged into a power strip). Darken the room, then turn on the TV while watching the screen carefully. If you see a horizontal section of the TV that is darker than the rest of the screen before the screen goes completely dark, that is where the bad LED strip is.

If none of the LEDs light up, even briefly, the problem may be a bad LED driver circuit. This is often part of the power supply board, but may be a separate board. The LED driver board is identifiable by being connected to a cable of three or more single wires (not twisted pairs or flat ribbon) going into the metal back pan of the TV, generally to the upper left side (viewed from the back). If the driver is separate from the power supply board, it will have another cable going to the power supply board..

Repairing a bad LED is labor-intensive.
1. Disconnect the TV from everything and remove the back cover. (at this point, you can plug in the set and repeat the LED test, and watch the various holes in the metal back pan to see if the LEDs flash when you turn on the set. Be very careful - there are exposed high voltage connections on the power supply board when the TV is plugged in, even if the set is off.
2. Make sure the TV is unplugged. Remove the shield from the T-Con board (at the top or bottom of the TV, centered horizontally).
3. Unlatch the flat cable connectors between the T-Con board and the edge of the LCD display.
4. Treat a section of clean carpet or large beach towel with anti-static spray, then lay it on a flat surface (make sure there are no foreign objects in this area; you don't want anything punching into the LCD). Lay the TV face down on this mat.
5. Remove the stand if it is still attached.
6. Remove all of the screws from the perimeter of the LCD. At this point, it is very desirable to have a helper. Lift the TV upright, holding it by both the front bezel and the metal back pan. Remove the front bezel (on most models it is held on by plastic tabs with hooks as well as some of the screws that were just removed).
7. Check for another set of screws that hold a rectangular steel frame or set of steel strips to the edge of the screen. Lay the TV flat again and remove these.
8. Very carefully unfold the connector strip(s) with the T-Con cables from the frame and lay them flat on the mat. Avoid any stress on the ribbons between the strips and LCD glass; if you tear or pull loose any of them, the display is ruined. Avoid touching any of the metal circuit tracing on the strips or the bare metal on the ends of the T-Con cables - static electricity discharge may damage the display.
9. Gently lift the back part of the TV (the metal pan with the circuit boards attached) off of the display. Two people are recommended for this task, especially for larger sets. On some models, it may be more workable to remove the LCD and diffuser sheets one part at a time while the TV is held upright. Make sure to keep all of the layers in the proper order, including front-side alignment, and put them on a clean lint-free surface.
10. There may be a white plastic reflector pan covering the LED strips in the back pan. The plastic is typically very thin and delicate. Carefully remove it.
11. Now you should have the LED strips exposed. At this point, you can plug in the TV and turn it on while watching the LED strips. (Caution: there are exposed high voltages on the back of the TV. Do not touch the power supply board while the TV is plugged in!) You will see the good LED strips flash while one or two strips remain dark. The bad LED is on one of the dark strips.

At this point, you have several options: 1. Replace the entire set of LED strips. If one LED has been abused (excess current or static electricity), chances are others in the set are also damaged. 2. Replace just the failed strip(s); 3. Identify and replace the bad LED; or. 4. Replace all of the LEDs in the bad strip(s). The strips are usually held in place by double-sided tape or a tacky adhesive. LED replacement requires tools for soldering surface-mount devices. If there is a circular piece of white plastic tape around the LED, carefully peel it off and save it, and likewise pull off the lens that is glued on over the LED before attempting to remove the LED.

White LEDs are blue LEDs with yellow phosphor painted on top. Blue LEDs are more vulnerable to static damage than other colors due to their strained-crystal construction. Consequently, parts with blue or white LEDs should not be handled unless electrostatic discharge safety measures are practiced.

Sep 28, 2018 | Televison & Video

1 Answer

How do i tell if its the LED driver or the LED strips that have gone out?


Measure the voltage that goes into the lamps, should be 100 volts give or take, if you have it then the lamps are bad, also measure with the set off and turn it on and see if the voltage jumps up then drops off again, then you have bad lamps as well....also there is even more to the issue of no LEDs...there are a couple pins on some sets that tell the power board to turn on the circuitry to the LED section of the power supply...not all sets have that however

Jan 07, 2018 | Samsung Televison & Video

1 Answer

Led driver on lg led tv. Is the driver bad or the led light strip bad


Only way to find out is to take the panel apart and test the LED strips with a DC power supply

Nov 16, 2017 | LG Televison & Video

1 Answer

Samsung UN65EH6000FXZA (Version YH02)


There is three possibilities:
1. Defective back lights LED strip.
2. Defective LED driver section integrated in the main power supply.
3. the main board.

How to check it:
1. You need a LED back lights tester to check the strips, or open the panel, use a 3.7 V DC power supply to test each LED diode separately.
2. Use a multi meter to test the out put DC voltage from the connector to the LED strip between the + & - for each section, (like 1+/1-, 2+/2- etc.) it should read 140 - 220 V DC. (need power up the TV).
3. Un-plug the cable between the main board & the power supply, power up the TV, if you get the back lights light up, the main board is bad.

Aug 11, 2017 | Samsung Televison & Video

1 Answer

Samsung tv MODEL UN40F6300AFXZA


Please un-plug the cable between the main board & the power supply board, apply AC power to the TV, if the back light come on, that means the back lights & the power supply are OK, then you need to replace the main board; if the back lights does not light up, mostly the back light LED strip(s) is bad.

May 24, 2017 | Samsung Televison & Video

1 Answer

I have a LG 47ln5700 smart tv. The screen goes black but the sound still works. I replaced the LED strips and the tv worked for about 4 hours and then the same thing happened. Any suggestions?


Bad power supply board can burn out those led strips. Recommend replacing both board and strips at same time. Lg 47LN5700 UH TV Parts
You can order most of the parts here.

If you need further help, reach me via phone at https://www.6ya.com/expert/steven_a67ead41eb5fc62a

Jan 11, 2017 | LG Televison & Video

1 Answer

LG model 47LN5700-UH LED TV. There is a single thin vertical line on the screen. I have changed the LED/Power Supply board and LED strips. What might be causing the vertical line?


You have wasted your time and money. The LED power supply and LED strips are only the backlighting. The only thing that might fix is a situation where you have a blank screen with the sound working.

If you don't know what you're doing, DON'T OPEN THE TV UP TO FIX IT, THERE ARE HAZARDOUS VOLTAGES ON THE POWER SUPPLY BOARD, EVEN WEEKS AFTER THE TV IS UNPLUGGED!

If you don't know how to do it yourself, find some local Electronic repair shops, get quotes, try to find reviews on the shops.

Nov 26, 2016 | LG Televison & Video

2 Answers

LG 50ln5200-ub led TV . Has no picture but great sound . What is the problem ? I did the flashlight test and can see the faint picture which tells me the backlighting is out . This tv model is a Black...


usually bad power supply, Where did you source your part? return/exchange it. Bad LEDs/ possible but not as likely, Tcon working if you can see images with flashlight. You must also have backlight on signal from main board ,check for 3 to 5v on labeled connecter on power supply. UPDATE---47" & 50" LN series. This model has had LED problems if your TV acts as described by Mr. Hughes in is answer to this problem you have bad LEDs

Feb 16, 2015 | LG 50 Inch LED TV 50LN5200 LN5200 Series...

2 Answers

I got a 55 inch Samsung flat panel tv model # UN55D6000Sf Version H302 with standby light blinking 1 time in repeat. I have changed the power supply board, main board & tcon board but still no luc


These blinks [flashes] are fault indication (Error Codes). From the number of blinks occur at one time switch ON, you can get an idea about the faulty circuit section inside it. This will make repair easy. These are called blinking codes. Make sure about the exact number of blinking of the standby/power LED, by switching On & OFF the set, for at least two times. Count it carefully. If you wish to get some details, check the site linked here. It has details about blinking codes, and fault locating procedure, to many popular brand TVs and other devices. http://electronicshelponline.blogspot.com/
Blinking codes details to many popular brand TVs are given. Surf the site with patience.

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Jan 27, 2015 | Samsung UN Televison & Video

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